Secure Socket Layer (SSL) 3.0 Vulnerability
Date: 15 October 2014
The purpose of this Alert is to bring attention to a recently identified vulnerability in SSL version 3.0.
Details of a vulnerability in Secure Socket Layer (SSL) version 3.0 have been published by security researchers. SSL 3.0 is considered an obsolete and insecure protocol which is nearly 15 years old, but is still widely supported on client browsers and web servers for backward compatibility purposes. A known attack technique dubbed the “POODLE” (Padding Oracle On Downgraded Legacy Encryption) attack, may allow the plaintext of secure connections to be calculated by a network attacker via a man-in-the-middle (MITM) attack to steal information such as “secure” HTTP cookies when using the nondeterministic CBC (Cipher Block Chaining) padding.
Software vendors have not yet released patches to address this vulnerability but a workaround is available to temporarily mitigate this issue.
The National Vulnerability Database (NVD) provides a summary for each vulnerability and references to advisories, solutions and tools. CCIRC recommends monitoring this link closely for updates to vendor patches.
CCIRC recommends that system administrators identify their affected assets and potential interdependencies with their organization's critical services, and implement the mitigations described below. Public-facing web servers and client web browsers should be addressed as top priorities.
Web Servers and Client Browsers:
- Apply software patches as soon as they become available.
- Disable SSL 3.0 support, if possible.
- If SSL 3.0 is required for support of legacy web applications, either 1) disable Cipher Block Chaining (CBC) mode, if possible; or 2) implement the TLS_FALLBACK_SCSV workaround to avoid a downgrade to SSL 3.0. Details on how to implement the TLS_FALLBACK_SCSV can be found here: https://tools.ietf.org/html/draft-ietf-tls-downgrade-scsv-00
Note to Readers
In support of Public Safety's mission to build a safe and resilient Canada, CCIRC's mandate is to help ensure the security and resilience of the vital non-federal government cyber systems that underpin Canada's national security, public safety and economic prosperity. As Canada's computer security incident response team, CCIRC is Canada's national coordination centre for the prevention and mitigation of, preparedness for, response to, and recovery from cyber incidents on non-federal government systems. It does this by providing authoritative advice and support, and coordinating information sharing and incident response.
Please note, CCIRC PGP key has recently been updated.
For general information, please contact Public Safety Canada's Public Affairs division at:
Telephone: 613-944-4875 or 1-800-830-3118
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